Valveless pump, particularly for fused salts or metals



I Nov. 13, 1962 A. v. DE? PAVA 3,063,930 I VALVELESS PUMP, PARTICULARLYFOR FUSED SALTS 0R METALS Filed Dec. 26, 1957 z Sheets-Sheet 1 F g. 3INVENTOR.

3 Sheets-Sheet 2 A. V. DE" PAVA VALVELESS PUMP, PARTICULARLY FOR FUSEDSALTS 0R METALS FIG. 4

Nov. 13, 1962 Filed Dec. 26, 1957 FIG. 8

Nov. 13, 1962 A. v. DE' PAvA VALVELESS PUMP, PARTICULARLY FOR FUSEDSALTS OR METALS Filed Dec. 26, 1957 3 Sheets-Sheet 3 FIGS FIG.6

r m L r FIG .7

3,063,930 Patented Nov 13, 1962 3,0fi3,930 VALVELESS PUMP, PARTICULARLYFOR FUSED SALTS R METALS Alberto Vajna de Pava, Milan, Italy, assignorto Montecatini, Societal Generale per ilndustria Mineraria e Cnimica,Milan, Italy, a corporation of Italy Filed Dec. 26, 1957, Ser. No.705,373

Claims priority, application Italy Dec. 27, 1956 15 Claims. (Cl. 204244)The present invention relates to a system comprising a force pumpparticularly suited for lifting and conveying, through conduits, (liquidsubstances which due to their chemical aggressivity or elevatedtemperature (e.g. 1000 C.) do not permit utilization of pumps of aconventional kind, provided with valves or other mobile closing members.The latter would not be suited for correct operation, whether employedin continuous or discontinuous contact, with such substances, sincethere would occur frequent blocking, due to partial cooling down of themolten substance, or corrosion of the pump elements.

From the above it follows that a pump for lifting metals or salts in themolten state should be characterized by maximum simplicity. In themajority of cases the purpose is to overcome heads and to providedeliveries of modest magnitude only, with the greatest possible safetyin operation. Good volumetric efficiency of the pump becomes ofrelatively lesser importance.

It is an object of the present invention to provide a force pump whichis essentially constituted by only two elements: a cylinder or pumpbody, and a piston, valves or other mobile elements being dispensedwith.

Without limiting the scope of the present invention there will now bedescribed in detail the structure and principle of operation of a pumpconstructed according to a preferred embodiment of the presentinvention. In the drawing:

FIG. 1 is a vertical section taken at line A A of FIG. 3. The piston isat the upper end of its stroke;

FIG. 2 is a vertical section on the same plane as in FIG. 1. In FIG. 2the piston is at the lower end of its downward stroke;

FIG. 3 is a composite of two left and right horizontal sections, theleft being taken at AA' in FIG. 1, and the right being at BB in FIG. 1.

FIGS. 4 to 8 illustrate the assembly of the valveless pump in thenecklace type multicell alumina electrolysis furnace described in thecopending applications of De Varda and Calabria mentioned below;

FIG. 4 is a transverse section taken at the left end portion of FIG. 7,but with the modification that only one pump is employed;

FIG. 5 is a longitudinal section taken at 55 of FIG. 7 (unmodified);

FIG. 6 is a longitudinal section taken at 66 of FIG. 7 (unmodified);

FIG. 7 is a plan view of the multicell furnace; and

FIG. 8 is a transverse section taken at the left end of FIG. 7.

The pump comprises an elongated cylindrical housing or chamber Carranged with its longer axis vertical, or if desired, inclined. Thechamber is closed at bottom. The vertical part of the cylinder isprovided, at convenient height, with one or more ports 1 for admissionof liquid.

During operation the pump should be placed with its bottom submerged inthe liquid to be lifted and the latter should have a level L higher thansaid admission port or ports.

In chamber C is a reciprocating piston S driven by means of conventionalconnecting rod and crank members, not shown in the drawing, forsimplicity. The

solid piston S is of cylindrical shape and has formed in its lateralsurface one or more grooves 2 parallel to the axis. The length of groove2 should be equal to the intended head of the pump, preferably.

Between the pump body and the piston there should be a slight play, tobe determined in accordance with the nature of the material of which thepump is made and with the kind of liquid that is to be lifted.

When the reciprocating piston has reached the upper dead point (see FIG.1), its bottom end is at a level higher than the port or ports 1employed for admission of the liquid to be lifted. The liquid can thusenter the lower part of the pump body and fill it.

As soon as the piston starts its downward stroke, the admission port orports for the liquid in the cylindrical chamber are closed by saidpiston. Hence the liquid is pushed towards the sole outlet available,constituted by the vertical groove or grooves 2 provided in the pistonwill, up to the upper end of said groove or grooves.

When the piston is at the lower dead point, the upper end of the grooveor grooves 2 will be at a certain height of the pump body. At thatheight (see FIG. 2) the cylindrical chamber is provided with a circularchannel 3 for collecting the liquid, the channel being connected to anoutlet member 4 having a discharge orifice. The channel prevents furtherrise of the liquid between the cylinder C and the piston.

The circular channel 3 functions as a collector, enabling the pumpedliquid to be collected without rising further between the cylindricalchamber and the piston.

The chamber containing the liquid to be lifted is indicated at D. It isto be understood that chamber D of FIG. 1 is representative only, sincein many applications (see FIGS. 4 to 8) the pump is used to raise moltenliquid from a lower level in a sealed chamber such as D to a higherlevel in a second chamber also sealed from the atmosphere. The secondchamber may have a bottom higher than that of the first chamber, toserve as the supply vessel for a gravity feed system. The molten liquidcan spill from the outlet 4 onto inclined surface E from which it passesto the second chamber (not shown in FIG. 1, but described below withreference to FIGS. 4 to 8).

Employing the same principle of operation, thegroove or grooves 2 in thelongitudinal surface of the piston may be dispensed with in some cases.To supply the liquid to be lifted with the necessary path for'rising,free play may be provided between the piston and cylinder ampler thanwould be necessary for the hydraulic seal between the two members. Thepath or play may be provided by suitably profiling the piston over aheight equal to the head desired. The play itself serves as a spacepermitting the rising of a film or thin flowing layer of the liquid tothe desired level. The centering between piston and pump body is ensuredby the minimum play existing between the two members in the upper zoneof the piston.

In similar cases however the piston will be provided along itslongitudinal axis, in correspondence with the port or ports for liquidadmission, with as many ribs or projecting reliefs as there are ports,destined to provide the closing of said ports at the predetermined time,and which aid said centering.

To attain the best operative efficiency, the reciprocating movement tobe imparted to the piston, should not be synchronous in the two stagesof rising and descent of the piston. That is, periods of stay of thelatter at the-two dead points, the upper and lower, should not be equaland should not be instantaneous. The movement instea should have thefollowing characteristics:

(a) The rising of the piston should be comparatively slow and of longerduration, as compared with the movement of descent. For instance, therising should be with a speed equal to 20-30% of the total duration ofone cycle of the piston.

(b) There should be a comparatively long stay of the piston at the upperdead point, to enable the liquid to enter through the admission portsand to fill the lower circular chamber. This stay should have a durationgenerally equal to 50-70% of the total duration of one cycle of thepiston.

(c) The descent of the piston should be with a comparatively rapidvelocity as compared with the afore-said rising movement, with aduration equal, for example, to about 10% of the total duration of onepiston cycle.

In practice a reciprocating movement having the aforesaidcharacteristics is readily provided through control cams of conventionaldesign (not shown).

The theoretical delivery of the pump at each stroke is determined by thevolume of the cylindrical chamber, up to the leve of the admission port1, less the volume of the vertical groove or grooves provided in thepiston wall.

To make the principle of construction and operation of the pump of theinvention more readily understandable, FIG. 3 of the appended drawingsindicates two horizontal sections of the pump. The left half section(taken along A A of the pump body is at the height of the inlet portsfor the liquid. The right half is a section (taken along BB) of the pumpbody at the height of the collecting channel and of the discharge portfor the liquid.

Due to its extreme constructive simplicity the pump can be built of anymaterial selected to fulfill special operating requirements.

The liquids to be lifted, the temperatures and the surronndings in whichthe pump is to be employed determine the nature of the materials to beused. The carbon steels permit operation at a temperature of 450-500 C.Some stainless steels, such as a strongly alloyed steel having anaustenitic structure, such as type A181 310 standards (25% Cr, 20% Ni),may be employed to advantage, up to temperatures of the order of 800900'C., for lifting liquids which do not display chemical aggressivityagainst the said steels.

Among the special steels having a high content of non-ferrous elementsthere may be selected, to advantage, alloys of the type of commercialHastelloy (60% Ni, 20% Mo. 18-20% Fe), or alloys of the Multimet type(N-155) based on Cr, Ni, Co, Fe, and others.

Among the non-metallic materials which due to resistance to hightemperatures and chemical inertness to the liquids to be lifted, forinstance fused salts, are suited for the making of the pumps, arecarbonaceous materials such as compact carbon agglomerates, and aboveall graphite.

In the field of utilizable materials defined as refractories proper arethe silico-aluminous materials having a structure as compact aspossible, as well as refractories of special type, such as metal oxidestreated at high temperatures, for example sinterized A1 sinterized MgO,etc.

In the case of pumps built with said non-metallic materials it isobvious that said materials will be employed only for the making of thepump body and piston. The latter then will be rigidly connected with asuitable metallic rod which serves for the purpose of connecting saidpiston mechanically with the drive members enabling to actuate the pump.In the accompanying drawings, which are only diagrammatical, said rodhas not been represented.

If the liquid to be lifted is to be maintained at an elevatedtemperature for the purpose of avoiding solidification, the pump may beprovided with or coated with a suitable heating jacket within which anappropriate fluid is circulated, or it may contain, incorporated withthe thickness of the body, a system of electric resistors convenientlyinsulated, or said resistors may be merely wound up externally aroundthe pump body, if the latter is made of a material which is a good heatconductor. For the sake of simplicity, the heating systems herementioned have not been indicated in the accompanying drawings.

According to a further embodiment of the invention, the pump whichitself has no heating members, may be accommodated in and be operated inthe vessel or chamber containing the liquid at high temperature (forexample 1000 C.) to be lifted. In such case, the stiff metallic rodcontrolling the piston will be conveniently extended outside saidchamber, which of course is provided with a heat-insulating coating orlining, to enable connection with suitable mechanical drive membersplaced outside.

Merely by way of example, but without limitative intent, there aregiven, with numerical data, some applications of pumps constructed inaccordance with the invention, for lifting molten metals or salts ofvarious kinds.

Example 1 The liquid to be lifted comprised a fused fluorinated bath,with suitable additions, and containing dissolved therein from 3 to 9%of aluminum oxide. Said bath was similar to those conventionally usedwith furnaces for the production of aluminum metal by fused saltelectrolysis. The operating temperature was about 940 C., that is, atemperature quite higher than the critical temperature at which the bathattains such a viscosity as to render its passage diflicult throughchannels or pipings. Said bath, in the specific case of the presentexample, was to be lifted from the lower chamber to the higher chamberin a necklace type multicell furnace substantially as described in G. DeVarda U.S. application Serial No. 587,985, filed May 29, 1956 (nowPatent 2,952,592), and G. Calabria U.S. application 670,785, filed July9, 1957 (now Patent 2,991,240). The total level difference to beovercome was cm. To ensure bath circulation with a maximum of 200ml./sec. in the circuit of the furnace now mentioned, there weredirectly installed in the interior of the lower chamber, in which wasmaintained an atmosphere substantially deprived of 0 two twin pumps inaccordance with the constructional and operational principles set forthhereinbefore, each of which possessed dimensions and characteristics ashereinafter defined: The material was graphite. The inner diameter ofthe lower cylindrical chamber was 62 mm. The piston stroke was 200 mm.,which signifies a total volume of the lower cylindrical chamber equal to600 ml. The piston moving in the interior of the pump was provided withtwo vertical grooves 2, diametrically opposed, of 800 mm. length and 0.5sq. cm. cross-section, each having a total volume of 80 ml. With thesespecifications, the theoretical delivery of one single pump was 520 ml.per pump shot. Considering the clearance volume and the minor losses dueto the play between piston and cylinder, there was in practice a usefuldelivery of about 450 ml. per pump shot, with a volumetric efiiciency ofEach of the two pumps was driven with a timing of 12 to 13 pump shotsper minute, thus providing an effective delivery unit of ml. per second,which proved to be sufficient for the desired purpose. The mechanicalpower absorbed for the operation of each individual pump proved to bevery low and, at any rate, such as not to cause any worry with respectto possible, vibrations and, therefore, the mechanical resistance of thematerial of which the pump was made, was not prejudiced or lowered underthe severe operating conditions required. Owing to the characteristicsof the necklace type multicell furnace, continuous operation of thepumps was not needed, and in the various intervals of rest and startingno disturbances or troubles arose, such as would have been due toblocking or other reasons. The twin pumps can be operated so as to raiseliquid alternatively or at the same time.

assass n Example 2 A pump quite analogous in its constructional andoperational principle, to the pump of Example 1, was built of carbonsteel and was designed to lift molten lead that had to be fed at thetemperature of 350 C. to a reactor, for the production of alead-and-sodium alloy. A level difference of 140 cm. was to be overcome.The pump was accommodated with its bottom submerged in an amplecrucible, wherein the lead was held at the desired temperature, andsheltered from air. The pump body was heated in this case by an electricresistor externally wound around said body and conveniently insulated,which ensured for the whole pump a uniform temperature of 350 C.

The internal surfaces designed to contact each other, the piston andinternal surface of the pump body, had been ground so as to be able toslide easily with a play of the order of 0.2 mm. With a volume of thelower cylindrical chamber equal to 1000 ml. and a volume of the twogrooves provided at diametrically opposed regions in the piston, of 280ml. (cross-section 1 sq. cm. each), the theoretical delivery was 720 ml.per pump shot. With a frequency of 20 shots per minute, considering theclearance volume, the actual lift of molten lead was about 13 liters,which is equal to 130-140 kg. per minute. The pump proved able to workunder such conditions continuously, even for 5 to 6 hours, without theslightest inconvenience.

Example 3 A pump analogous to that mentioned in Example 1 was made ofgraphite, but the volume of its lower cylindrical chamber was 700 ml. Itwas used to lift molten aluminum coming from the collecting pocket of afurnace for fused salt electrolysis and destined to be conveyed to aningot mould. In this case the whole pump body was kept at a temperatureof 700 -C., which is necessary to enable easy lifting of the aluminum inthe molten state. The heating was by means of a system of electricresistors, housed with suitable heatand electricinsulation withinspecial grooves provided in the thickness of the pump body. As a matterof fact, in this case it was not possible to house the whole pump, as inExample 1, in a closed chamber, and the contrivance now described had tobe resorted to, to obtain the desired temperature. The difference inlevel to be overcome was 120 cm. The piston of the pump was providedwith a single groove of 1 sq. cm. cross-section. The theoreticaldelivery was 580 ml. per pump shot. The actual delivery was 500 ml. pershot, that is, the volumetric efliciency was of the order of 86%. Thepump was driven in discontinuous manner, that is, with periods of rest,at a frequency of shots per minute. Thereby quite regular lifting ofmolten aluminum at a rate of 8 litres (i. e. about kg.) per minute wasattained, which is considered satisfactory, considering thetechnological requirements of transfer of molten metal from a furnace toan ingot mould.

It is to be understood that, in its specific application as part of atransfer means for a gravity system of a molten bath electrolytecirculatory system in multicell electrolytic furnaces, the piston andpump cylinder can be used in place of the liquid transfer meansdescribed in the application Serial No. 670,785 mentioned above. Theorifice 4 can supply the molten material directly to the upper chamberor to a conveying conduit or sloped surface E connecting thelower-bottomed chamber to the upper-bottomed chamber of the gravitysystem.

This transfer system is illustrated in FIGS. 4 to 8, which are nowdescribed. Like numerals and letters designate the same elements as inFIG. 1 to 3.

Referring to FIG. 4, the pump piston S is provided with an operatingmechanism B, including an eccentric drive g. The pump cylinder C has twolower liquid intakes at 1 and 5. The molten liquid raised from liquid 6body 8 is fed by spout 4' to the sloping ledge surface 41; At 4 2 is areturn conduit for overflow from upper chamber 7 to lower chamber 6.Chambers 6 and '7 are provided with overflow outlets 60 and 70. FIG. 8is substantially like FIG. 4, the difference being that two pumps areemployed in FlG. 8, as mentioned above. The two pumps are also shown inF168. 6 and 7.

FIG. 7 is a plan view of the furnace. The pumps shown in chamber 6, atthe left end, raise the molten cryolite bath from which the liquid flowsthrough passages 11 provided in the upper parts of each of the terminalelectrodes 131 and 132 (FIG. 5) and of each of the intermediate bipolarelectrodes 130. The bath liquid circulates through the necklace ofcells, through passages 11 and 11 (FIGS. 6 and 7), being replenishedwith alumina introduced at 111 and 112. The larger fixed covers for thefurnace are indicated in FIG. 7, but removable covers ususally used forelectrolysis gaps 10 are not shown. carbonaceous anode 131 is providedwith embedded electric conductors 14. Carbonaceous cathode electrode 132is likewise provided with embedded conductors 12.

I claim:

1. A valve-less force pump system for raising corrosive, hot, moltenliquids, comprising means providing an outer chamber for liquid, apiston force pump device in the chamber, said device comprising ahousing having a closed bottom end, said device further comprising anupwardly-downwardly extending recirprocating piston loosely fitted insaid housing with play sutficient to permit the rising of a thin flowinglayer of said liquid between said piston and said housing duringdownward movement of said piston, an inlet port for the liquid in thelower side portion of the housing at a distance above the bottom endthereof, the piston opening and closing the inlet port in its strokecycle, said piston device having an upwardly extending open surfacegroove for upward flow of liquid from a chamber formed in the lowerportion of the housing when the piston is moved downwardly to force theliquid upwardly, said housing being provided with outlet means for flowof the raised liquid therefrom and having in its upper portion aperipheral passageway communicating with said groove and with saidoutlet means for reception of the raised liquid and for passing it tosaid outlet means.

2. A valve-less force pump system for raising corrosive, hot, moltensubstances, comprising means providing an outer chamber for liquid, apiston force pump device in the chamber, said device comprising ahousing having a closed bottom end, said device further comprising anupwardly-downwardly extending reciprocating piston loosely fitted insaid housing with play sufficient to permit the rising of a thin flowinglayer of said liquid between piston and said housing during downwardmovement of said piston, an inlet port for the liquid in the lower sideportion of the housing at a distance above the bottom end thereof, thepiston opening and closing the inlet port in its stroke cycle, saidpiston device having an upwardly extending open surface groove forupward flow of liquid from a chamber formed in the lower portion of thehousing when the piston is moved downwardly to force the liquidupwardly, said housing being provided with outlet means for flow of theraised liquid therefrom and having in its upper portion a peripheralpassageway communieating with said groove and with said outlet means forreception of the raised liquid and for passing it to said outlet means,said passageway comprising an inner peripheral channel formed in thehousing wall at a height equal to the proposed head of the raised liquidabove the level in the said outer chamber.

3. A valve-less force pump system for raising hot, corrosive, moltensubstances, comprising means providing an outer chamber for liquid, apiston force pump device in the chamber, said device comprising ahousing having a closed bottom end, said device further comprising anupwardly-downwardly extending reciprocating piston loosely fitted insaid housing with play sufficient to permit the rising of a thin flowinglayer of said liquid between said piston and said housing duringdownward movement of said piston, an inlet port for the liquid in thelower side portion of the housing at a distance above the bottom endthereof, the piston opening and closing the inlet port in its strokecycle, said piston device providing therein an upwardly extendingpassage for upward flow of liquid from a chamber formed in the lowerportion of the housing when the piston is moved downwardly, said passagecomprising an open groove formed in the lateral surface of the piston,said housing providing in its upper portion a passageway communicatingwith said passage for reception of liquid from the latter, thepassageway comprising an inner peripheral channel formed in the housingwall at a height equal to the proposed head of the raised liquid abovethe level in the said outer chamber, said passageway having an exitmeans for passage of the raised liquid therefrom, the upper end of thegroove being substantially at the level of the channel when the pistonis at lower dead end position.

4. The system defined in claim 1, the housing and piston being ofgraphite, the system being suitable for use at 700 C. for lifting moltenaluminum.

5. The system defined in claim 1, the housing and piston being of carbonsteel, the system being suitable for use up to 450 C.

6. The system defined in claim 1, for use at high temperatures forpumping corrosive liquids, the housing and the piston being of stainlesssteel.

7. A valve-less force pump system for raising hot, corrosive, moltensubstances, comprising means providing an outer chamber for liquid, apiston force pump device in the chamber, said device comprising ahousing, said device further comprising an upwardly-downwardly extendingreciprocating piston loosely fitted in said housing with play sumcientto permit the rising of a thin flowing layer of said liquid between saidpiston and said housing during downward movement of said piston, aninlet port for the liquid in the lower side portion of the housing at adistance above the bottom end thereof, said housing being closed belowsaid inlet port, said piston device providing therein an upwardlyextending passage for upward flow of liquid from a chamber formed in thelower portion of the housing when the piston is moved downwardly, saidpassage comprising an open groove formed in the lateral surface of thepiston, the groove being off-set peripherally from the inlet port, saidhousing providing in its upper portion a passageway communicating withsaid groove for reception of liquid from the latter, the passagewaycomprising an inner peripheral channel formed in the housing wall at aheight equal to the proposed head of the raised liquid above the levelin the said outer chamber, said passageway having an exit means forpassage of the raised liquid therefrom, the upper end of the groovebeing substantially at the level of the channel when the piston is atlower dead end position, said inlet port being below but closelyadjacent to the lower end of the piston when the latter is at the end ofits upper stroke, whereby when the piston arrives at its upper endposition the inlet port is opened and when it starts its downward strokeit closes the inlet port.

8. The apparatus defined in claim 1, said means providing an outerchamber for liquid comprising enclosure means in which the housing andpiston are enclosed and isolated from the atmosphere, the enclosuremeans having temperature maintenance means to prevent solidification ofthe liquid, drive means for reciprocating the piston outside theenclosure means, and a metal rod connected to the piston and extendingoutside the enclosure means in operative connection with the drivemeans.

9. A high temperature apparatus comprising a structure providing aprocessing zone containing a hot, corrosive, molten material, andproviding two chambers for the molten material, a first one of thechambers communicating with the processing zone to receive the moltenmaterial therefrom, and the second communicating with the processingzone to return molten material thereto, each having a liquid head, theliquid head of the second chamber being higher than that of the firstchamber, said molten material being caused to circulate by gravity fromsaid second chamber, through the processing zone and back to said firstchamber, by differences in liquid head between the processing zone andthe said two chambers, a valve-less apparatus to transfer moltenmaterial from the first chamber to the second, comprising a piston forcepump device disposed in said first chamber, said device comprising apiston housing and an upwardly-downwardly reciprocating piston looselyfitted in said housing, an inlet port for the molten material in thelower portion of the housing, said piston housing having a closed bottomend below said inlet port, the piston opening and closing the inlet portduring its operating cycle, said piston device having an upwardlyextending surface groove for upward flow of molten material from achamber formed in the lower portion of the housing when the piston ismoved downwardly to push the material up wardly, said piston housingproviding in its upper portion a passageway communicating with saidgroove for reception of molten material from the latter, said passagewayhaving an exit means for passage of the raised molten material to thesecond chamber.

10. An apparatus comprising a structure providing a processing zonecontaining a molten liquid, and providing two chambers for liquid, afirst one of the chambers communicating with the processing zone toreceive molten liquid therefrom, and the second communicating with theprocessing zone to return liquid thereto, means for maintaining a liquidhead in the second chamber higher than that in the first chamber, saidbath being caused to circulate by gravity from said second chamber,through the processing Zone and back to said first chamber, bydifferences in liquid head between the processing zone and the said twochambers, a valve-less apparatus to transfer liquid from the firstchamber to the second, comprising a piston force pump device disposed insaid first chamber, said device comprising a piston housing in saidchamber, an upwardly-downwardly reciprocating piston loosely fitted insaid housing with play sufficient to permit the rising of a thin flowinglayer of said liquid between said piston and said housing duringdownward movement of said piston, an inlet port for the liquid in thelower side portion of the housing, said piston housing having a closedbottom end below said inlet port, said piston having an upwardlyextending open surface groove for upward flow of liquid from a chamberformed in the lower portion of the housing when the piston is moveddownwardly to force the liquid in the chamber upwardly, said groovebeing offset peripherally with respect to the inlet port, said housingproviding in its upper portion a passageway communicating with saidgroove for reception of liquid from the latter, the passagewaycomprising an inner peripheral channel formed in the housing wall, saidpassageway having an exit means for passage of the raised liquid to thesecond chamber, said inlet port being below but closely adjacent to thelower end of the piston when the latter is at the end of its upperstroke, whereby when the piston arrives at its upper dead end positionthe inlet port is opened and when it starts its downward stroke itcloses the inlet port, the upper end of the groove of the piston beingsubstantially at the level of the peripheral channel when the piston isat lower dead end position.

11. A valveless force pump system for lifting molten fluorine compounds,comprising means providing a closed outer chamber for the molten liquid,a piston force pump device in the chamber, said device comprising ahousing of graphite having a closed bottom end, said device furthercomprising an upwardly-downwardly extending reciprocating, graphitepiston loosely fitted in said housing with play sufficient to permit therising of a thin flowing layer of said liquid between said piston andsaid housing during downward movement of said piston, an inlet port forthe liquid in the lower side portion of the housing at a distance abovethe bottom end thereof, said housing being closed below said port, thepiston opening and closing the inlet port in its operating cycle, saidpiston device having an upwardly extending surface groove for upwardfiow of liquid from within the lower portion of the housing when thepiston is moved downwardy to force liquid upwardly, said housing beingprovided in its upper portion with a peripheral passageway communicatingwith said groove for reception of liquid from the latter, saidpassageway having an exit means for passage of the lifted liquidtherefrom.

12. An electrolysis furnace comprising a heat-insulated structurecontaining a plurality of electrolytic cells, the cells containing amolten bath to be electrolyzed and opposed cathodes and anodes, theinsulated structure providing two adjacent chambers therein, a first oneof said chambers communicating with a cell to receive molten bath liquidtherefrom, and the second communicating with another cell to returnmolten bath liquid thereto, each chamber having a liquid head, theliquid head of the second chamber being higher than that of the firstchamber, said bath being caused to circulate by gravity among the cellsduring the electrolysis, from said second chamber, through the cells,and back to said first chamber, by difierences in head between thevarious cells and the said two chambers, a communicating duct in saidinsulated structure between the two chambers, the duct communi catingwith the first chamber above the liquid level of the latter, anapparatus in said insulated structure to transfer molten bath liquidfrom the first chamber to the second, comprising a piston pressure pumpdevice in the first chamber, said device comprising a housing andfurther comprising an upwardly-downwardly extending reciprocating pistonloosely fitted in said housing with play sufiicient to permit the risingof a thin flowing layer of said liquid between said piston and saidhousing during downward movement of said piston, an inlet port for theliquid in the lower side portion of the housing at a distance above thebottom end thereof, said housing being closed below said port, saidpiston having a groove formed in its lateral surface providing anupwardly extending passage for upward flow of liquid from the lowerportion of the housing when the piston is moved downwardly, the groovebeing peripherally offset from the inlet port, said housing beingprovided in its upper portion with a passageway communicating with saidgroove for reception of liquid from the latter, said passagewaycomprising an inner peripheral channel formed in the housing wall at aheight equal to the proposed head of the raised liquid above the levelin the said chamber, said passageway having an exit means for passage ofthe raised liquid therefrom to the second chamber.

13. A valve-less force pump system for lifting molten lead, comprisingmeans providing an outer chamber for molten lead, a piston force pumpdevice in the chamber, said device comprising a housing, said devicefurther comprising an upwardly-downwardly extending reciprocating pistonloosely fitted in said housing with play sufficient to permit the risingof a thin flowing layer of said liquid between said piston and saidhousing during downward movement of said piston, an inlet port for themolten lead in the lower side portion of the housing at a distance abovethe bottom end thereof, said housing being closed below said inlet port,said piston having formed therein an upwardly extending open surfacegroove for upward flow of molten lead from within the lower portion ofthe housing when the piston is moved downwardly to force lead upwardly,said groove being displaced with respect to the inlet port, said housingbeing provided in its upper portion with a passageway communicating withsaid groove for reception of liquid from the latter, said passagewaycomprising an inner peripheral channel formed in the housing wall at aheight equal to the proposed head of the raised liquid above the levelin the said chamber, said passageway having an exit means for passage ofthe raised liquid therefrom.

14. The apparatus defined in claim 12, the pump housing and piston beingof graphite.

15. The apparatus defined in claim 12, the pump housing and piston beingof stainless steel.

References Cited in the file of this patent UNITED STATES PATENTS732,169 Chapman June 30, 1903 2,250,164 Minden July 22, 1941 2,451,492Johnson Oct. 19, 1948 2,528,210 Stewart Oct. 3.1, 1950 FOREIGN PATENTS319,487 Germany Mar. 9, 1920

1. A VALVE-LESS FORCE PUMP SYSTEM FOR RAISING CORROSIVE, HOT, MOLTENLIQUIDS, COMPRISING MEANS PROVIDING AN OUTER CHAMBER FOR LIQUID, APISTON FORCE PUMP DEVICE IN THE CHAMBER, SAID DEVICE COMPRISING AHOUSING HAVING A CLOSED BOTTOM END, SAID DEVICE FURTHER COMPRISING ANUPWARDLY-DOWNWARDLY EXTENDING RECIRPROCATING PISTON LOOSELY FITTED INSAID HOUSING WITH PLAY SUFFICIENT TO PERMIT THE RISING OF A THIN FLOWINGLAYER OF SAID LIQUID BETWEEN SAID PISTON AND SAID HOUSING DURINGDOWNWARDLY MOVEMENT OF SAID PISTON, AN INLET PORT FOR THE LIQUID IN THELOWER SIDE PORTION OF THE HOUSING AT A DISTANCE ABOVE THE BOTTOM ENDTHEREOF, THE PISTON OPENING AND CLOSING THE IN-